Just a question from a begginer :
In the simulation of a solar or (galactic) system, when you calculate the position of a planet P at time t+dt, you only know the position of the other bodies in the system at time t, so you calculate the distance d between P and any other body Q at time t...
Yet another formula for pi(x) (prime number counting function)
start with wilson's therorem : p is prime iff p divides (p-1)! + 1
let G(x) be the gamma function
then p is prime iff sin(pi*(G(x)+1)/x) = 0
let f be the function x -> sin(pi*(G(x)+1)/x)
Since f(x) = sin(pi*G(x)/x+pi/x) and...